1. Field of the Invention
The present invention relates to a dielectric ceramic material, in particular, a dielectric ceramic material suitable for electronic components used in the high-frequency bands such as the microwave band and the millimeter wave band.
2. Description of the Related Art
The dielectric ceramic materials disclosed in Patent Documents 1 to 4 have been known as dielectric ceramic materials high in dielectric constant and high in the Q value in the high-frequency bands.
The dielectric ceramic materials disclosed in Patent Document 1 each include as the main constituents TiO2: 22 to 43 wt %, ZrO2: 38 to 58 wt % and SnO2: 9 to 26 wt %, wherein the dielectric ceramic materials each further include ZnO in an additive amount of 7 wt % or less and NiO in an additive amount of 10 wt % or less. The main constituents are represented by a general formula (Zr, Sn) TiO4. In Patent Document 1, when the content of TiO2 is less than the above described range, the relative dielectric constant εr is decreased, and when the content of TiO2 is larger than the above described range, the temperature property of the resonance frequency becomes too large on the plus side. When the content of ZrO2 is less or larger than the above described range, the temperature property of the resonance frequency becomes too large on the plus side. Further, when the content of SnO2 is less than the above described range, the temperature property of the resonance frequency becomes too large on the plus side and the Q value is decreased, and when the content of SnO2 is larger than the above described range, the temperature property of the resonance frequency becomes too large on the minus side. Furthermore, when the contents of ZnO and NiO are respectively larger than the above described ranges, the Q value is decreased.
For the purpose of further increasing the Q value than those of the dielectric ceramic materials disclosed in Patent Document 1, Patent Document 2 has proposed to further add 7 wt % or less of Ta2O5 to the dielectric ceramic material disclosed in Patent Document 1, and Patent Document 3 has proposed to further add 5 wt % or less of Nb2O5 to the dielectric ceramic material disclosed in Patent Document 1.
Additionally, Patent Document 4 has proposed to add 3 to 20 wt % of a glass containing at least B and Si in relation to the total weight of the main constituents disclosed in Patent Document 1, with a prerequisite that the firing temperature is as low as 1100° C. or lower, for the purpose of obtaining a dielectric ceramic material high in dielectric constant, large in the Q value and low in the temperature property of the resonance frequency.
Patent Document 1: Japanese Patent Publication No. 55-34526
Patent Document 2: Japanese Patent Publication No. 4-59267
Patent Document 3: Japanese Patent Publication No. 5-6762
Patent Document 4: Japanese Patent Laid-Open No. 2001-220230